Netflix's growth in international markets and its large investment in content will boost its shares, according to one Wall Street firm.

KeyBanc Capital Markets reiterated its overweight rating on Netflix shares, predicting strong subscriber numbers for the company this year.

"We see Netflix as the global leader in subscription video in the internet era and continue to recommend owning Netflix," analyst Andy Hargreaves wrote in a note to clients Thursday. "Updated broadband household estimates drive international subscriber expectations higher. … We expect solid 4Q results and see the potential for upside to subscriber estimates through 2018."

The analyst noted a recent report from the International Telecommunication Union that revealed broadband internet access was rising worldwide faster than expected. That makes Netflix's potential market bigger and "prompts a corresponding increase to our estimates for Netflix's international subscribers in 2018 and beyond," Hargreaves wrote.

As a result, he increased his 2018 global net subscriber forecast for Netflix to 20.6 million from 19.3 million.

Hargreaves said Netflix's large scale and content library will enable the company to beat its competition and produce subscriber growth and profitability "well ahead of current expectations."

Netflix is one of the market's best-performing stocks. Its shares have rallied 59 percent in the past 12 months versus the S&P 500's 24 percent gain.